The present invention relates to railroad track lifting and aligning clamping devices of the type that are provided on railroad tamping machines, primarily upon machines which can work on tangent track and in switches.
Examples of the type of device to which the present invention relates are seen in U.S. Pat. No. 4,111,128; British Pat. No. 1,416,693; British Pat. No. 1,493,153 (corresponding to U.S. Pat. No. 3,968,752); French Patent application No. 81 08595 (publication no. 2,483,481); United Kingdom patent application GB No. 2035423A (corresponding to U.S. Pat. No. 4,323,013 and French No. 79 26767 publication no. 2442914). Examples of other devices of interest to this general art are seen in British patent nos. 1,264,057; 1,540,199; U.S. Pat. No. 3,690,263 and Swiss Pat. no. 624,625.
Generally speaking the devices of the prior art have been complex in the nature in which the rail lifting hooks can be adjusted to accommodate for changes in rail height and lateral position. Such changes may be brought about by lateral displacement in switches, or in rail height because of rail head wear. Also changes of cross-section at rail joints represent changes of rail configuration. Sometimes also it is desired to grasp under the base of the rail rather than the rail head. Although efforts have been made to simplify the construction of the prior art devices, a great many of them still have defects. For example in certain types, if the rail engaging hooks slip in a "production" lifting mode the whole lifting and aligning frame is pulled clear of the track. In other words, a positive lock of the lining clamp has been difficult to achieve under the great variety of rail cross-sections encountered during work on tangent track, jointed track and track in the area of switches. Time then has to be spent readjusting the frame into position before rapid production can continue. This type of disengagement is common also when working on worn rail, or when working on two different rail sizes, or in switches. Lining contact is frequently lost and when the lining force is applied either the rail is not lined or the lining devices may be damaged.
Applicant seeks to simplify the construction of a rail clamp which can operate satisfactorily in a production, or in a switch correcting, mode, which is simple to maintain and relatively cheap to manufacture and which is positive in its gripping and force transmitting qualities.